<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <div id="app"></div>
</body>
<script src="./js/vue.js"></script>
<script>

    var App = {
        template:"<div id='app'>123</div>"
    }

    new Vue({
        el:"#app",
        components:{
            App:App
        },
        template:"<App></App>"
    })
</script>
</html>